Reproductive failure, including infertility and spontaneous abortion, is a growing concern to society. Psychosocial stress may be a significant, but treatable cause of reproductive failure. However, this association has been difficult to study prospectively in humans. Laboratory animals provide valuable models for establishing whether psychosocial stress can result in reproductive failure. Naturalistic studies provide models for establishing why particular socio-ecological conditions are perceived as stressful, as well as when and why such stress is likely to lead to reproductive failure. Studies of free-living animals have been constrained by (1) lack of noninvasive technique for evaluating physiologic condition and (2) limited longitudinal background data on individuals living in their natural environment. This study proposes to validate noninvasive techniques to measure biologically meaningful levels of reproductive and adrenal steroid hormones in feces of captive- maintained baboons. These techniques are being validated for the eventful use in a 10 year ongoing study on the behavioral ecology of reproductive failure in free-living yellow baboons at Mikumi National Park, Tanzania. Fecal material can be collected easily without disturbing stress- susceptible individuals; this makes fecal steroid measures a potentially valuable research tool for integrating endocrine function with naturally occurring environmental events. Validation studies will focus on five steroids: estradiol (E2), progesterone (P4), cortisol (C), dehydroepiandrosterone (DHEA), and testosterone (T). E2, P4 and T concentrations provide measures of reproductive function in females and males. C, DHEA, and T provide measures of adrenal activation, including that associated with the stress response. The proposed studies will: 1) identify fecal and urinary metabolites of E2, P4, C, DHEA and T, as well as respective excretion rates after radiolabel infusion; 2) correlate longitudinal fecal steroid excretion profiles with blood hormone secretory patterns, urinary steroid metabolite excretion and visual reproductive markers (e.g. menstruation and sex skin turgesence) during natural reproductive cycles and after acute challenges with exogenous hormones (ACTH and GnRH); 3) develop indices of nonspecific steroid excretion rate, particularly those associated with GI tract transit time; 4) test the influence of dietary fiber on fecal steroid excretion rate and the potential of eliminating any existing effects using nonspecific steroid rate indices; 5) determine if fecal P4 excretion following time-mating is a useful indicator of early pregnancy or spontaneous abortion; and 6) expand fecal preservation techniques for use in the field. If proven valid, these excreted steroid techniques could provide an important noninvasive tool for interrelating reproductive function and adrenal activation with naturally occurring socio-ecological events. Such events could markedly improve our understanding of the complex relationships between biology, health and behavior in free-living primates.